Magnet assembly

ABSTRACT

A magnet assembly ( 200 ) is provided according to the invention. The magnet assembly ( 200 ) includes at least one magnet ( 210 ), a magnet keeper ( 220 ) including a substantially planar magnet receiving face ( 222 ) for receiving the at least one magnet ( 210 ), and brazing ( 230 ) that affixes the at least one magnet ( 210 ) to the magnet receiving face ( 222 ) of the magnet keeper ( 220 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnet assembly, and moreparticularly, to a magnet assembly for a high temperature application.

2. Statement of the Problem

It is known to use Coriolis mass flow meters to measure mass flow,density, and volume flow and other information of materials flowingthrough a pipeline as disclosed in U.S. Pat. No. 4,491,025 issued to J.E. Smith, et al. of Jan. 1, 1985 and Re. 31,450 to J. E. Smith of Feb.11, 1982. These flow meters have one or more flow tubes of differentconfigurations. Each conduit configuration may be viewed as having a setof natural vibration modes including, for example, simple bending,torsional, radial and coupled modes. In a typical Coriolis mass flowmeasurement application, a conduit configuration is excited in one ormore vibration modes as a material flows through the conduit, and motionof the conduit is measured at points spaced along the conduit.

The vibrational modes of the material filled systems are defined in partby the combined mass of the flow tubes and the material within the flowtubes. Material flows into the flow meter from a connected pipeline onthe inlet side of the flow meter. The material is then directed throughthe flow tube or flow tubes and exits the flow meter to a pipelineconnected on the outlet side.

A driver applies a force to the flow tube. The force causes the flowtube to oscillate. When there is no material flowing through the flowmeter, all points along a flow tube oscillate with an identical phase.As a material begins to flow through the flow tube, Coriolisaccelerations cause each point along the flow tube to have a differentphase with respect to other points along the flow tube. The phase on theinlet side of the flow tube lags the driver, while the phase on theoutlet side leads the driver. Sensors are placed at different points onthe flow tube to produce sinusoidal signals representative of the motionof the flow tube at the different points. The phase difference betweenthe two sensor signals is proportional to the mass flow rate of thematerial flowing through the flow tube or flow tubes.

A flowtube driver typically comprises a coil that is opposed by a fixedmagnet. The coil and the fixed magnet are attached to a pair offlowtubes or a flowtube and a balance beam. In operation, the magneticfield in the driver coil is rapidly alternated. The fixed, opposingmagnet assists in generating oscillating forces that alternativelybrings the flowtube(s) together and apart.

Likewise, a pickoff sensor of a flow meter can comprise a magnetic coilpickup and an opposing magnet, with one or both being attached toflowtubes, as described above. In operation, the magnetic coil pickupgenerates a substantially sinusoidal signal from the moving magnet whenthe flowtube(s) is oscillating.

A flow meter can be used to measure a flow material in a hightemperature application. Some flow meter applications require continuoususe in temperatures at or above 400 degrees Fahrenheit. In the priorart, magnets used for the driver and/or pickoff sensor assemblies areheld in a magnet keeper by means of a shrink fit. The magnet keeper isattached to a flow tube.

In the prior art, Aluminum-Nickel-Cobalt (AlNiCo) magnets are used inhigh temperature applications where flow tube stiffness is low andresulting vibrational amplitudes are high. A drawback in using AlNiComagnets is that AlNiCo magnets have relatively higher masses than othermagnet technologies while their B-field strength is relatively low.However, in newer flow meter designs, stiffness is high and vibrationalamplitudes are low. As a consequence, newer flow meter designs requirelow mass driver and pickoff systems in order to operate properly. Simplyresorting to larger magnets is not practical because the spacing betweenbrackets is fixed by the design of the flow meter.

SUMMARY OF THE SOLUTION

The above and other problems are solved and an advance in the art isachieved through the provision of a magnet assembly according to anyembodiment of the invention.

A magnet assembly is provided according to an embodiment of theinvention. The magnet assembly comprises at least one magnet, a magnetkeeper including a substantially planar magnet receiving face forreceiving the at least one magnet, and brazing that affixes the at leastone magnet to the magnet receiving face of the magnet keeper.

A magnet assembly is provided according to an embodiment of theinvention. The magnet assembly comprises at least one magnet, a magnetkeeper for receiving the at least one magnet, a countersink regionformed in the magnet keeper, with the countersink region beingconfigured to receive the at least one magnet, and brazing that affixesthe at least one magnet in the countersink region of the magnet keeper.

A magnet assembly is provided according to an embodiment of theinvention. The magnet assembly comprises at least one magnet, a magnetkeeper including a substantially planar magnet receiving face forreceiving the at least one magnet, and a nickel-plating layer thataffixes the at least one magnet to the magnet receiving face of themagnet keeper.

A method of forming a magnet assembly is provided according to anembodiment of the invention. The method comprises placing at least onemagnet onto a magnet keeper. The magnet keeper includes a substantiallyplanar magnet receiving face for receiving the at least one magnet. Themethod further comprises brazing the at least one magnet to the magnetkeeper. The magnet keeper is adapted to be affixed to the vibratory flowmeter.

A method of forming a magnet assembly is provided according to anembodiment of the invention. The method comprises placing at least onemagnet onto a magnet keeper. The magnet keeper includes a substantiallyplanar magnet receiving face for receiving the at least one magnet. Themethod further comprises nickel-plating the at least one magnet to themagnet keeper. The magnet keeper is adapted to be affixed to thevibratory flow meter.

ASPECTS OF THE INVENTION

In one aspect of the magnet assembly, the at least one magnet comprisesa samarium cobalt magnet.

In another aspect of the magnet assembly, the at least one magnetcomprises a nickel-plated samarium cobalt magnet.

In yet another aspect of the magnet assembly, the magnet receiving facecomprises a countersink region formed in the magnet keeper, with thecountersink region being configured to receive the at least one magnet.

In yet another aspect of the magnet assembly, the magnet assemblyfurther comprises a pole piece that is affixed to the at least onemagnet.

In yet another aspect of the magnet assembly, the magnet assemblyfurther comprises a pole piece that is affixed to the at least onemagnet, with the pole piece including a brazing aperture.

In one aspect of the method, the at least one magnet comprises asamarium cobalt magnet.

In another aspect of the method, the at least one magnet comprises anickel-plated samarium cobalt magnet.

In yet another aspect of the method, the magnet receiving face comprisesa countersink region formed in the magnet keeper, with the countersinkregion being configured to receive the at least one magnet.

In yet another aspect of the method, the method further comprisesaffixing a pole piece to the at least one magnet.

In yet another aspect of the method, the method further comprisesre-magnetizing the magnet assembly.

DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings.

FIG. 1 shows a flow meter comprising a meter assembly and meterelectronics.

FIG. 2 shows a magnet assembly for a vibratory flow meter according toan embodiment of the invention.

FIG. 3 is a section view AA of the magnet assembly of FIG. 2.

FIG. 4 shows the magnet assembly according to an embodiment of theinvention.

FIG. 5 is a section view BB of the magnet assembly of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-5 and the following description depict specific examples toteach those skilled in the art how to make and use the best mode of theinvention. For the purpose of teaching inventive principles, someconventional aspects have been simplified or omitted. Those skilled inthe art will appreciate variations from these examples that fall withinthe scope of the invention. Those skilled in the art will appreciatethat the features described below can be combined in various ways toform multiple variations of the invention. As a result, the invention isnot limited to the specific examples described below, but only by theclaims and their equivalents.

FIG. 1 shows a flow meter 5 comprising a meter assembly 10 and meterelectronics 20. Meter assembly 10 responds to mass flow rate and densityof a process material. Meter electronics 20 is connected to meterassembly 10 via leads 100 to provide density, mass flow rate, andtemperature information over path 26, as well as other information. ACoriolis flow meter structure is described although it is apparent tothose skilled in the art that the present invention could be practicedas a vibrating tube densitometer without the additional measurementcapability provided by a Coriolis mass flow meter.

Meter assembly 10 includes a pair of manifolds 150 and 150′, flanges 103and 103′ having flange necks 110 and 110′, a pair of parallel flow tubes130 and 130′, drive mechanism 180, temperature sensor 190, and a pair ofvelocity sensors 170L and 170R. Flow tubes 130 and 130′ have twoessentially straight inlet legs 131 and 131′ and outlet legs 134 and134′ which converge towards each other at flow tube mounting blocks 120and 120′. Flow tubes 130 and 130′ bend at two symmetrical locationsalong their length and are essentially parallel throughout their length.Brace bars 140 and 140′ serve to define the axis W and W′ about whicheach flow tube oscillates.

The side legs 131, 131′ and 134, 134′ of flow tubes 130 and 130′ arefixedly attached to flow tube mounting blocks 120 and 120′ and theseblocks, in turn, are fixedly attached to manifolds 150 and 150′. Thisprovides a continuous closed material path through Coriolis meterassembly 10.

When flanges 103 and 103′, having holes 102 and 102′ are connected, viainlet end 104 and outlet end 104′ into a process line (not shown) whichcarries the process material that is being measured, material enters end104 of the meter through an orifice 101 in flange 103 and is conductedthrough manifold 150 to flow tube mounting block 120 having a surface121. Within manifold 150 the material is divided and routed through flowtubes 130 and 130′. Upon exiting flow tubes 130 and 130′, the processmaterial is recombined in a single stream within manifold 150′ and isthereafter routed to exit end 104′ (connected by flange 103′ having boltholes 102′) to the process line (not shown).

Flow tubes 130 and 130′ having substantially the same Young's modulusare selected and appropriately mounted to the flow tube mounting blocks120 and 120′ so as to have substantially the same mass distribution,moments of inertia and system stiffness about bending axes W-W andW′-W′, respectively. These bending axes go through brace bars 140 and140′. Inasmuch as the Young's modulus of the flow tubes change withtemperature, and this change affects the calculation of flow anddensity, resistive temperature detector (RTD) 190 can be mounted to flowtube 130′, to continuously measure the temperature of the flow tube. Thetemperature of the flow tube and hence the voltage appearing across theRTD for a given current passing therethrough is governed by thetemperature of the material passing through the flow tube. Thetemperature dependent voltage appearing across the RTD is used in a wellknown method by meter electronics 20 to compensate for the change inelastic modulus of flow tubes 130 and 130′ due to any changes in flowtube temperature. The RTD is connected to meter electronics 20 by lead195.

Both flow tubes 130 and 130′ are driven by driver 180 in oppositedirections about their respective bending axes W and W′ and at what istermed the first out-of-phase bending mode of the flow meter. This drivemechanism 180 may comprise any one of many well known arrangements, suchas a magnet mounted to flow tube 130′ and an opposing coil mounted toflow tube 130 and through which an alternating current is passed forvibrating both flow tubes. A suitable drive signal is applied by meterelectronics 20, via lead 185, to drive mechanism 180.

Meter electronics 20 receives the RTD temperature signal on lead 195,and the left and right velocity signals appearing on leads 165L and165R, respectively. Meter electronics 20 produces the drive signalappearing on lead 185 to drive element 180 and vibrate tubes 130 and130′. Meter electronics 20 processes the left and right velocity signalsand the RTD signal to compute the mass flow rate and the density of thematerial passing through meter assembly 10. This information, along withother information, is applied by meter electronics 20 over path 26 toutilization means 29.

FIG. 2 shows a magnet assembly 200 according to an embodiment of theinvention. The magnet assembly 200 includes at least one magnet 210 anda magnet keeper 220. In one embodiment, the magnet assembly 200 is usedin a meter assembly 10 of a vibratory flow meter 5. The vibratory flowmeter 5 can comprise a Coriolis flow meter or a vibrating densitometer,for example.

The magnet 210 is part of a flow meter driver assembly 180 or part of aflow meter pickoff sensor 170 (see FIG. 1). The magnet 210 in theembodiment shown is substantially cylindrical. However, other magnetshapes can be employed.

The magnet 210 can comprise one or more component magnets. The magnet210 can comprise a stack of component magnets that are brazed together,for example.

The magnet 210 in one embodiment comprises a samarium cobalt (SmCo)magnet. A SmCo magnet substantially retains its magnetic properties athigh temperatures and therefore is advantageous in use with a flow meterthat receives a high temperature flow material. For example, at or above400 degrees Fahrenheit, a SmCo magnet can generate a satisfactory levelof the magnetic flux needed to operate in a flow tube driver or flowtube pickoff sensor. However, it should be understood that other magnetmaterials can be used and are within the scope of the description andclaims, such as an AlNiCo magnet, for example.

The magnet keeper 220 can comprise one or more keeper componentportions. The magnet keeper 220 includes a magnet receiving face 222that receives the magnet 210. The magnet receiving face 222 in oneembodiment is substantially planar. The magnet keeper 220 can furtherinclude a wall 224 and a mounting feature 226. The wall 224 can surroundthe magnet 210, but does not contact the magnet 210. A gap G existsbetween the magnet 210 and the wall 224 (see FIG. 3), wherein acorresponding portion of the driver or sensor component can move intoand out of this gap G. The wall 224 therefore can operate to constrainthe magnetic flux to a region approximately between the magnet 210 andthe corresponding driver or sensor component.

It should be understood that the wall 224 is not a required portion ofthe magnet keeper 220. The magnet keeper 220 can comprise just a base ofsome manner, wherein the gap G is formed between the magnet 210 andother components.

In one embodiment, the magnet 210 is nickel-plated. The nickel-platinglayer extends over at least a portion of the magnet 210 and over atleast a portion of the magnet receiving face 222 of the magnet keeper220. The nickel-plating improves a high temperature performance of aSmCo magnet. In addition, the nickel-plating can provide some or all ofthe affixing. For example, in one embodiment of forming the magnetassembly 200, the magnet 210 is placed on the magnet receiving face 222and then the entire magnet assembly 200 is nickel-plated. The subsequentnickel-plating in this embodiment affixes the magnet 210 to the magnetkeeper 220.

This figure also shows an optional pole piece 211 that is affixed to themagnet 210. The pole piece 211 can comprise an additional magnet.Alternatively, the pole piece 211 can comprise a magnetically conductivematerial that functions to shape or conduct the magnetic flux from themagnet 210 to the wall 224. The pole piece 211 can include an aperture212 that provides an opening for brazing (or otherwise affixing) thepole piece 211 to the magnet 210. In addition, the pole piece 211 canfurther include a rim 213 that substantially fits over the magnet 210.

FIG. 3 is a section view AA of the magnet assembly 200 of FIG. 2. Thesection view shows brazing 230 that affixes the magnet 210 to the magnetreceiving face 222 of the magnet keeper 220. The brazing 230 comprisesjoining similar or dissimilar metals using a melted filler metal.Brazing often uses a filler metal that includes some bronze. However,brazing can use a variety of metals, including copper, nickel, zinc,silver, and phosphorus. Brazing does not melt the base metal piece(s)being brazed, but instead the melted filler metal is distributed bycapillary action. At its liquid temperature, the molten filler metalinteracts with a thin layer of the base metal, cooling to form anexceptionally strong, sealed joint due to grain structure interaction.Brazing typically requires temperatures of 900 to 2200 degreesFahrenheit, although some consider brazing to include temperatures aslow as 450 degrees Fahrenheit.

This figure further shows detail of the mounting feature 226 accordingto an embodiment of the invention. The mounting feature 226 in theembodiment shown includes an attachment aperture 228. The attachmentaperture 228 can be used to affix or removably affix the magnet keeper220 to a flow tube or flow tube structure. The attachment aperture 228in the embodiment shown includes threading that can receive some mannerof threaded fastener. However, it should be understood that theattachment aperture 228, and indeed the entire mounting feature 226, canaffix to a flow meter structure in any manner.

FIG. 4 shows the magnet assembly 200 according to an embodiment of theinvention. In this embodiment, the magnet receiving face 222 includes acountersink region 229 that is configured to receive the magnet 210. Thecountersink region 229 aids in aligning and assembling the magnet. Thecountersink region 229 can advantageously function to center the magnet210 on the magnet keeper 220. In addition, the countersink region 229can provide more area for brazing the magnet 210 to the magnet keeper220.

FIG. 5 is a section view BB of the magnet assembly 200 of FIG. 4. Thesection view shows the magnet 210 seated in the countersink region 229.The brazing 230 affixes the magnet 210 into the countersink region 229and to the magnet keeper 220. As can be seen from the figure, thecountersink region 229 can be substantially planar. It can also be seenfrom the figure that the countersink region 229 can substantially matchthe shape of the magnet 210. In addition, the countersink region 229 caninclude any manner of grooving 234 that provides extra brazing volume.Alternatively, the grooving 234 can comprise any manner of ridging,roughening, texturing, etc.

The magnet assembly 200 according to any of the embodiments can beconstructed in various ways. In one method, the magnet 210 is placedagainst the magnet receiving face 222 of the magnet keeper 220 andbrazed in place. In another method, the magnet 210 is place within thecountersink region 229 of the magnet keeper 220 and brazed in place. Inanother method, the uncharged magnet is plated into place as a means ofaffixing the parts together. The brazed or plated assembly can then besubjected to a re-magnetization process. The re-magnetization processcan be performed in order to substantially restore magnetic capacitythat is lost due to the heat of the brazing process.

The magnet assembly according to the invention can be employed accordingto any of the embodiments in order to provide several advantages, ifdesired. The invention provides a high-temperature magnet assembly for avibratory flow meter. The invention provides a high-temperature magnetassembly for a flow tube driver system or for a flow tube sensor system.The invention provides a strong and effective magnet mount for avibratory flow meter. The invention provides a high-temperature magnetassembly using a samarium cobalt magnet. The invention provides ahigh-temperature magnet assembly using a nickel-plated samarium cobaltmagnet. The invention provides a magnet mount for a samarium cobaltmagnet, wherein the magnet mount does not exert a compression force onthe magnet. The invention provides a high-temperature magnet assemblywithout increasing the size of the magnet.

1. A magnet assembly (200), comprising: at least one magnet (210); amagnet keeper (220) including a substantially planar magnet receivingface (222) for receiving the at least one magnet (210) and a wall (224)extending generally perpendicularly away from the planar magnetreceiving face (222) to define a gap (G) between the at least one magnet(210) and the wall (224); a countersink region (229) formed in themagnet receiving face (222) of the magnet keeper (220) and spaced fromthe wall (224), with the countersink region (229) being configured toreceive the at least one magnet (210); and brazing (230) that affixesthe at least one magnet (210) in the countersink region (229) of themagnet keeper (220).
 2. The magnet assembly (200) of claim 1, with theat least one magnet (210) comprising a samarium cobalt magnet.
 3. Themagnet assembly (200) of claim 1, with the at least one magnet (210)comprising a nickel-plated samarium cobalt magnet.
 4. The magnetassembly (200) of claim 1, further comprising a pole piece (211) that isaffixed to the at least one magnet (210).
 5. The magnet assembly (200)of claim 1, further comprising a pole piece (211) that is affixed to theat least one magnet (210), with the pole piece (211) including a brazingaperture (212).
 6. The magnet assembly (200) of claim 1, with thecountersink region (229) including grooving (234).
 7. A magnet assembly(200), comprising: at least one magnet (210); a magnet keeper (220)including a substantially planar magnet receiving face (222) forreceiving the at least one magnet (210); a pole piece (211) affixed tothe at least one magnet (210) and substantially opposite the magnetreceiving face (222); and a nickel-plating layer that affixes the atleast one magnet (210) to the magnet keeper (220) and to the pole piece(211).
 8. The magnet assembly (200) of claim 7, with the at least onemagnet (210) comprising a samarium cobalt magnet.
 9. The magnet assembly(200) of claim 7, with the magnet receiving face (222) comprising acountersink region (229) formed in the magnet keeper (220), with thecountersink region (229) being configured to receive the at least onemagnet (210).
 10. The magnet assembly (200) of claim 7, with the polepiece (211) including a brazing aperture (212).
 11. The magnet assembly(200) of claim 7, with the countersink region (229) including grooving(234).
 12. A method of forming a magnet assembly, comprising: placing atleast one magnet onto a magnet keeper, with the magnet keeper includinga substantially planar magnet receiving face including a countersinkregion configured for receiving the at least one magnet and a wallextending generally perpendicularly away from the planar magnetreceiving face and spaced from the countersink region; and affixing theat least one magnet in the countersink region of the magnet keeper,wherein the magnet keeper is adapted to he affixed to a vibratory flowmeter.
 13. The method of claim 12, with the at least one magnetcomprising a samarium cobalt magnet.
 14. The method of claim 12, withthe affixing comprising brazing or nickel-plating the at least onemagnet in the countersink region.
 15. The method of claim 12, furthercomprising affixing a pole piece to the at least one magnet.
 16. Themethod of claim 12, further comprising re-magnetizing the magnetassembly.
 17. The method of claim 12, with the countersink regionincluding grooving.
 18. A magnet assembly (200), comprising: at leastone magnet (210); a magnet keeper (220) including a substantially planarmagnet receiving face (222) for receiving the at least one magnet (210)and a wall (224) extending generally perpendicularly away from theplanar magnet receiving face (222) to define a gap (G) between the atleast one magnet (210) and the wall (224); a countersink region (229)formed in the magnet receiving face (222) of the magnet keeper (220) andspaced from the wall (224), with the countersink region (229) beingconfigured to receive the at least one magnet (210); and anickel-plating layer extending over substantially the entire magnetassembly (200) and affixing the at least one magnet (210) in thecountersink region (229) of the magnet keeper (220).
 19. The magnetassembly (200) of claim 18, with the at least one magnet (210)comprising a samarium cobalt magnet.
 20. The magnet assembly (200) ofclaim 18, further comprising a pole piece (211) that is affixed to theat least one magnet (210).
 21. The magnet assembly (200) of claim 18,further comprising a pole piece (211) that is affixed to the at leastone magnet (210), with the pole piece (211) including a brazing aperture(212).
 22. The magnet assembly (200) of claim 18, with the countersinkregion (229) including grooving (234).